Thermoplastic molding compositions of vinyl aromatic compound α,β unsaturated cyclic anhydride copolymers

ABSTRACT

Novel thermoplastic molding compositions are disclosed which comprise a copolymer of a vinyl aromatic compound with an α,β-unsaturated cyclic anhydride and a hydrogenated A-B-A block copolymer or a block copolymer of the A&#39;-B&#39;-A&#39; type or an acrylic graft polymerization copolymer with or without a polyphenylene ether resin.

This is a division of application Ser. No. 935,919 filed Aug. 23, 1978,which in turn is a division of application Ser. No. 477,435 filed June7, 1974, now U.S. Pat. No. 4,124,654.

This invention relates to thermoplastic molding compositions that arebased on a copolymer of a vinyl aromatic compound with anα,β--unsaturated cyclic anhydride and a hydrogenated, A-B-A blockcopolymer or a block copolymer of the A'-B'-A' type or an acrylic graftpolymerization copolymer with or without a polyphenylene resin.

BACKGROUND OF THE INVENTION

The term "polyphenylene ether resin" includes a family of polymers wellknown to those skilled in the art, they are made by a variety ofcatalytic and noncatalytic processes from the corresponding phenols orreactive derivatives thereof. By way of illustration, certain of thefollowing polyphenylene ethers are discussed in Hay, U.S. Pat. Nos.3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. Nos. 3,257,357 and3,257,358. Also, the Bennett and Cooper patents, U.S. Pat. Nos.3,639,656, 3,642,699 and 3,661,848 describe processes for thepreparation of polyphenylene ethers. Other disclosures relating toprocesses using metal-amine catalysts are found in Bussink et al, U.S.Pat. No. 3,337,449; Blanchard et al, U.S. Pat. No. 3,219,626; Laakso etal, U.S. Pat. No. 3,342,892; Borman, U.S. Pat. No. 3,344,166; Hori etal, U.S. Pat. No. 3,384,619; Faurote et al, U.S. Pat. No. 3,400,217; anddisclosures relating to metal based catalysts which do not includeamines, are well known from patents such as Wieden et al, U.S. Pat. No.3,442,885 (copper-amidines); Nakashio et al, U.S. Pat. No. 3,573,257(metal-alcoholate or phenolate); Kobayashi et al, U.S. Pat. No.3,455,880 (cobalt chelates); and the like. In the Stamatoff patents, thepolyphenylene ethers are produced by reacting the correspondingphenolate ion with an initiator, such as peroxy acid salt, an acidperoxide, a hypohalite, and the like, in the presence of a complexingagent. Disclosures relating to non-catalytic processes, such asoxidation with lead dioxide, silver oxide, etc., are described in Priceet al, U.S. Pat. No. 3,382,212. All of the patents which are mentionedabove are incoporated herein by reference.

The Cizak patent, U.S. Pat. No. 3,383,435 discloses blends ofpolyphosylene ether resins and styrene resins. The thermoplasticcompositions disclosed by Cizak may include rubber-modified styreneresin, as well as crystal polyamine. The Carmelite, Kramer and Lee, Jr.patent, U.S. Pat. No. 3,787,532, also discloses polyphenylene ethercontaining compositions. These patents are also incorporated byreference.

U.S. Pat. No. 3,660,531 discloses compositions of a polyphenylene etherstyrene resin and a styrene-butadiene-styrene block copolymer. Thesecompositions have a major proportion of polyphenylene ether polymer.

There have been many attempts to upgrade the heat distortion temperatureand the impact resistance of vinyl aromatic resins. One approach hasbeen to provide copolymers of the vinyl aromatic compounds withα,β-unsaturated cyclic anhydrides. In the case of styrene-maleicanhydride copolymers, a level of 20% of maleic anhydride increases theheat distortion temperature but the resulting material is very brittle.

Accordingly, it is a principal object to provide improved compositionsof vinyl aromatic resins that have higher heat distortion temperaturesand better impact strengths particularly as measured in terms of theGardner impact tests.

DESCRIPTION OF THE INVENTION

According to the present invention, there is provided a composition thatis useful in the manufacture of thermoplastic molded articles. Thesethermoplastic molding compositions comprise:

(a) from 40-95 parts by weight, preferably from 40-80 parts by weight ofa copolymer of a vinyl aromatic compound and an α,β-unsaturated cyclicanhydride;

(b) from 5-40 parts by weight, preferably 10-30 parts by weight of ablock copolymer selected from the group consisting of:

i. hydrogenated block copolymers of the A-B-A type wherein prior tohydrogenation; A is a polymerized mono-alkenyl aromatic hydrocarbonblock; B is a polymerized conjugated diene hydrocarbon block; the blocksA constituting 2-50 weight percent of the copolymer and the unsaturationof block B having been reduced by hydrogenation.

ii. block copolymers of the A'-B'-A' type wherein A is a polymerizedmono-alkenyl aromatic hydrocarbon block and B' is a polymerizedconjugated diene block, the block B' being of higher molecular weightthan that of the combined molecular weight of terminal blocks A';

iii. emulsion graft polymerization product of an acrylic monomer aloneor in admixture with a styrene monomer on a rubbery diene homopolymer orstyrene-diene copolymer backbone; and

iv. mixtures of the foregoing; and

(c) from 0-50 parts by weight, preferably 0-40 parts by weight of apolyphenylene ether resin.

The preferred compositions will include 5-20 parts by weight of thepolyphenylene ether resin. The PPO containing compositions will have aratio of the copolymer of the vinyl compound and the α,β-unsaturatedcyclic anhydride to polyphenylene ether resin that is greatr than one.The polyphenylene ether resins are preferably of the formula: ##STR1##wherein the oxygen ether atom of one unit is connected to the benzenenucleus of the next adjoining unit, n is a positive integer and is atleast 50, and each Q is a monovalent substituent selected from the groupconsisting of hydrogen, halogen, hydrocarbon radicals, halohydrocarbonradicals having at least two carbon atoms between the halogen atom andthe phenyl nucleus, hydrocarbonoxy radicals, and halohydrocarbonoxyradicals having at least two carbon atoms between the halogen atom andphenyl nucleus, said radicals being free of a tertiary alpha-carbonatom. The preparation of polyphenylene ether resins corresponding to theabove formula is described in the above-mentioned patents of Hay andStamatoff. Especially preferred polyphenylene ether resins for purposesof the present invention are those having alkyl substitution in the twopositions ortho to the oxygen ether atom--i.e., where each Q is alkyl,most preferably, having from 1 to 4 carbon atoms. The most preferredpolyphenylene ether resin for purposes of the present invention ispoly(2,6-dimethyl-1,4-phenylene) ether (each Q is methyl).

The copolymers of the vinyl aromatic compounds and the α,β-unsaturatedcyclic anhydride are well known and are described in the literature. Thevinyl aromatic component may be derived from compounds of the formula:##STR2## wherein R¹ and R² are selected from the group consisting oflower alkyl or alkenyl groups of from 1 to 6 carbon atoms and hydrogen;R³ and R⁴ are selected from the group consisting of chloro, bromo,hydrogen and lower alkyl of from 1 to 6 carbon atoms; R⁵ and R⁶ areselected from the group consisting of hydrogen and lower alkyl andalkenyl groups of from 1 to 6 carbon atoms or R⁵ and R⁶ may beconcatenated together with hydrocarbyl groups to form a naphthyl group.These compounds are free of any substituent that has a tertiary carbonatom. Styrene is the preferred vinyl aromatic compound. Theα,β-unsaturated cyclic anhydrides include maleic anhydride, citraconicanhydride, itaconic anhydride, aconitic anhydride and the like. Thepreferred α,β-unsaturated cyclic anhydride is maleic anhydride.

These polymers may comprise 40 to 1 mole percent of the α,β-unsaturatedcyclic anhydride and from 60 to 99 mole percent of a vinyl aromaticcompound. The preferred polymers will contain about 25-5 mole percent ofthe α,β-unsaturated cyclic anhydride and 75-95 mole percent of the vinylaromatic compound. The preparation of these copolymers are described inU.S. Pat. No. 2,971,939; U.S. Pat. No. 3,336,267 and U.S. Pat. No.2,769,804 which are hereby incorporated by reference.

With respect to the hydrogenated block copolymers of the A-B-A type,they are made by means known in the art and they are commerciallyavailable.

These materials are described in U.S. Pat. No. 3,421,323 to Jones, whichis hereby incorporated by reference.

Prior to hydrogenation, the end blocks of these copolymers comprisehomopolymers or copolymers preferably prepared from alkenyl aromatichydrocarbons and particularly vinyl aromatic hydrocarbons wherein thearomatic moiety may be either monocyclic or polycyclic. Typical monomersinclude styrene, alpha methyl styrene, vinyl xylene, ethyl vinyl xylene,vinyl naphthalene and the like or mixtures thereof. The end blocks maybe the same or different. The center block may be derived from, forexample, polyisoprene or polybutadiene.

The ratio of the copolymers and the average molecular weights can varybroadly although the molecular weight of center block should be greaterthan that of the combined terminal blocks. It is preferred to formterminal blocks A having average molecular weights of 4,000-115,000 andcenter block B e.g., a polybutadiene block with an average molecularweight of 20,000-450,000. Still more preferably, the terminal blockshave average molecuar weights of 8,000-60,000 while the polybutadienepolymer blocks has an average molecular weight between 50,000 and300,000. The terminal blocks will preferably comprise 2-50% by weight,or more preferably, 5-30% by weight of the total block polymer. Thepreferred copolymers will be those formed from a copolymer having apolybutadiene center block wherein 35-55%, or more preferably, 40-50% ofthe butadiene carbon atoms are vinyl side chains.

The hydrogenated copolymers may have the average unsaturation reduced tofrom 95 to 5% of the original value. It is preferred to have theunsaturation of the center block B reduced to 10%, or more preferably,5% of its original value.

The block copolymers are formed by techniques well known to thoseskilled in the art. Hydrogenation may be conducted utilizing a varietyof hydrogenation catalysts such as nickel or kieselguhr, Raney nickel,copper chromate, molybdenum sulfide and finely divided platinum or othernoble metals on a low surface area carrier.

Hydrogenation may be conducted at any desired temperature or pressure,from atmospheric to 300 p.s.i.g. the usual range being between 100 and1000 p.s.i.g. at temperatures from 75° F. to 600° F. for times between0.1 and 24 hours, preferably from 0.2-8 hours.

Hydrogenated block copolymers such as Kraton G-GXT-0650, KratonG-GXT-0772 and Kraton G-GXT-0782 from Shell Chemical Company, PolymersDivision have been found useable according to this invention.

With respect to the A'-B'-A' block copolymers, they may be made by meanswell known in the art and are also available commercially from a numberof sources.

Block copolymers of vinyl aromatic compounds and conjugated dienes aredescribed in Kennedy, et al Editor, Polymer Chemistry of SyntheticElastomers, Interscience, Vol. 23, Part II, 1969, pages 553-559. Ingeneral, they will be of the A-B-A' type in which the center and endblocks can vary. In the compositions of this invention, the centralblock B, will preferably be that of a conjugated diene, e.g., butadiene;isoprene; 1,3-pentadiene; 2,3-dimethyl-butadiene, and the like ormixtures of the foregoing. The terminal blocks A and A', will be thesame or different, but will always be derived from a vinyl aromaticcompound, e.g., sytrene, α-methyl styrene, vinyl toluene, vinyl xylene,vinyl naphthalene, or mixtures of any of the foregoing. In the mostpreferred compositions, the block copolymer will have terminal blocks Aand A' comprised of polystyrene and center block B comprised ofpolybutadiene.

The ratio of the comonomers can vary broadly, so long as the molecularweight center block is greater than that of the combined terminalblocks. Preferably, with the above limitation, the molecular weight ofthe terminal blocks each will range from about 2000 to about 100,000while that of the center block will range from about 25,000 to about1,000,000.

The block copolymers are made by an organometallic initiatedpolymerization process using, for example sodium or lithium metal anorganic derivative thereof. The diene monomers can be polymerized with amonofunctional or difunctional initiator, as is described in Kennedy etal, mentioned above.

In one process, the block copolymer is prepared by dissolving theconjugated diene, e.g., butadiene, in an aromatic hydrocarbon solvent,e.g., xylene, toluene, etc., and adding 0.3 to 7.5 millimoles/100 partsof monomer of an organodilithium initiator, e.g., dilithiobutane,dilithiostilbene, etc. Polymerization of the diene is completed and thenthe vinyl aromatic compound is added and polymerization of this iscompleted to form the block copolymer. The product is precipitated anddeactivated, e.g., with alcohol, such as ethanol or isopropanol andpurified by redissolving in hydrocarbon and reprecipitating withalcohol.

Full descriptive details of such a process are given in Zelinski, U.S.Pat. No. 3,251,905, incorporated herein by reference.

In another process, the block copolymer is built up sequentially using,e.g., a secondary or tertiary alkyl lithium compound at about 100-2000parts per million based on the total weight of the monomers and apolymerization temperature in the range 20°-65° C. For example, styreneis dissolved in cyclohexane at 32° C. and treated with 5530 parts permillion of secondary butyl lithium. After polymerization is complete,isoprene is injected and polymerization is continued at 55°-57° C.Finally styrene is added and the third block is polymerized. The productcan be recovered as described above. Full descriptive details of such aprocess are given in Holden et al, U.S. Pat. No. 3,231,635. Thesematerials are commercially available as Kraton resins.

The graft polymerization product of an acrylic monomer and a dienerubber preferably comprises (1) from about 20-80% by weight of abackbone polymer of the units of butadiene or butadiene and styrene,wherein the butadiene units are present in quantities of at least 40% byweight of the backbone polymer, (2) 80-20% by weight of an acrylicmonomer graft polymerized to (1); said acrylic monomer units beingselected from the group consisting of lower alkyl methacrylates,alicyclic methacrylates and alkyl acrylates, and (3) 0 to 60% by weightof a styrene monomer graft polymerized to (1) or (2); sequentially orsimultaneously with the polymerization of (2).

The graft polymerization product of an acrylic monomer alone or withstyrene monomer and the rubbery diene polymer or copolymer may beprepared by known techniques, typically by emulsion polymerization. Theymay be formed from a styrene-butadiene copolymer latex and a monomericmaterial such as methyl methacrylate alone or with another compoundhaving a single vinylidene group copolymerizable therewith, e.g.,styrene. For example, in the preparation of a representative material,85-65 parts by weight of monomeric methyl methacrylate or monomericmethyl methacrylate to the extent of at least 55% and preferably as muchas 75% by weight in admixture with another monomer which copolymerizestherewith, such as ethyl acrylate, acrylonitrile, vinylidene chloride,styrene, and similar unsaturated compounds containing a singlevinylidene group, is added to 15-35 parts by weight of solids in astyrene-butadiene copolymer latex. The copolymer solids in the latexcomprise about 10-50% by weight of styrene and about 90-50% by weight ofbutadiene and the molecular weight thereof is within the range of about25,000 to 1,500,000. The copolymer latex of solids in water contains adispersing agent such as sodium oleate or the like to maintain thecopolymer in emulsion. Interpolymerization of the monomer or monomericmixture with the copolymer solids emulsified in water is brought aboutin the presence of a free-radical generating catalyst and apolymerization regulator which serves as a chain transfer agent, at atemperature of the order of 15° C. to 80° C. Coagulation of theinterpolymerized product is then effected with a calcium chloridesolution, for instance, whereupon it is filtered, washed and dried.Other graft copolymers and differing from the above only in the ratio ofmonomeric material solely or preponderantly of methyl methacrylate tothe butadiene-styrene copolymer latex in the presence of which it ispolymerized extends from 85-25 parts by weight of the former to 15-75parts by weight of the latter. These materials may extend in physicalproperties from relatvely rigid compositions to rubbery compositions. Apreferred commercially available material is Acryloid KM 611 which issold by Rohm & Haas. Also, U.S. Pat. No. 2,943,074 and U.S. Pat. No.2,857,360, which are incorporated by reference, contain additionalinformation as to the preparation of these materials. A preferredmaterial is described in U.S. Pat. No. 2,943,074, column 4, preparation"D" and converted to emulsified polymer "B" as described therein.

The compositions of this invention will preferably include from 40-80parts of the copolymer of a vinyl aromatic compound and α,β-unsaturatedcyclic anhydride, and most preferably from 60-75 parts by weight of thismaterial. The block copolymer of the A-B-A type or A'-B'-A' type, or theacrylic graft polymerization product, will preferably be present at from10-40 parts by weight and most preferably at 20-30 parts by weight. Ifemployed, the polyphenylene ether resins are preferably present at alevel of from 1-40 parts by weight and preferably at a level of from5-30 parts by weight.

The compositions of the invention may also include reinforcing fillers,such as aluminum, iron or nickel, and the like, and non-metals, such ascarbon filaments, silicates, such as acicular calcium silicate,asbestos, titanium dioxide, potassium titanate and titanate whiskers,glass flakes and fibers. It is also to be understood that, unless thefiller adds to the strength and stiffness of the composition, it is onlya filler and not a reinforcing filler, as contemplated herein. Inparticular, the reinforcing fillers increase the flexural strength, theflexural modulus, the tensile strength and the heat distortiontemperature.

Although it is only necessary to have at least a reinforcing amount ofthe reinforcement present, in general, the combination of components (a)and (b) will comprise from about 10 to about 90 parts by weight and thefiller will comprise from about 10 to about 90 parts by weight of thetotal composition.

In particular, the preferred reinforcing fillers are of glass and it ispreferred to use fibrous glass filaments comprised of lime-aluminumborosilicate glass that is relatively soda free. This is known as "E"glass. However, other glasses are useful where electrical properties arenot so important, e.g., the low soda glass known as "C" glass. Thefilaments are made by standard processes, e.g., by steam or air blowing,flame blowing and mechanical pulling. The preferred filaments forplastics reinforcment are made by mechanical pulling. The filamentdiameters range from about 0.000112 to 0.00075 inch, but this is notcritical to the present invention.

In general, best properties will be obtained if the sized filamentousglass reinforcment comprises from about 1 to about 80% by weight basedon the combined weight of glass and polymers and preferably from about10 to about 50% by weight. Especially preferably the glass will comprisefrom about 10 to about 40% by weight based on the combined weight ofglass and resin. Generally, for direct molding use, up to about 60% ofglass can be present without causing flow problems. However, it isuseful also to prepare the compositions containing substantially greaterquantities, e.g., up to 70-80% by weight of glass. These concentratescan then be custom blended with blends of resins that are not glassreinforced to provide any desired glass content of a lower value.

The length of glass filaments and whether or not they are bundled intofibers and the fibers bundled in turn to yarns, ropes or rovings, orwoven into mats, and the like, are also not critical to the invention.However, in preparing the present compositions it is convenient to usethe filamentous glass in the form of chopped strands of from about 1/8"to about 1" long, preferably less than 1/4" long. In articles moldedfrom the compositions, on the other hand, even shorter lengths will beencountered because, during compounding, considerable fragmentation willoccur. This is desirable, however, because the best properties areexhibited by thermoplastic injection molded articles in which thefilament lengths lie between about 0.000005" and 0.125 (1/8").

It is a preferred feature of this invention also to provide flameretardant thermoplastic compositions of vinyl aromatic-α,β-unsaturatedcyclic anhydrides as defined above by modifying said compositions toinclude a flame-retardant additive in a minor proportion but in anamount at least sufficient to render the composition non-burning orself-extinguishing.

Particular flame retardants which may be used are well known and aredescribed in the literature.

The compositions may be prepared by tumbling the components, extrudingthe mixed powders into a continuous strand, dropping the strands intopellets and thereafter molding the pellets into the desired shape. Thesetechniques are well known to those skilled in this art and are not acritical feature of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is further illustrated in the following exampleswhich are set forth as further descriptions of the invention, but arenot to be construed as limiting the invention thereto.

EXAMPLE I

The compositions listed in Table 1 were prepared by compounding thecomponents on a 28 mm. W.P. extruder at a feed temperature of 550° F., arear temperature of 570° F., a front temperature of 580° F., and a dietemperature of 590° F. The materials were molded on a 3 oz. Newburyinjection molding machine at 400° F. cylinder temperature and 130° F.mold temperature. The cycle time was 35 seconds.

                                      TABLE 1                                     __________________________________________________________________________    Sample No.          1.sup.a                                                                         2 3 4 5.sup.a                                                                         6 7 8 9 10.sup.a                                                                        11.sup.a                                                                          12.sup.a                                                                          13.sup.a                                                                          14                                                                              15                                                                              16                                                                              17                                                                              18.sup.a          __________________________________________________________________________    Components (parts by                                                          weight except where noted)                                                    I  poly(2,6-dimethyl-1,4-phenylene)                                              ether (PPO General Electric Co.)                                                               --                                                                              --                                                                              10                                                                              10                                                                              10                                                                              --                                                                              --                                                                              10                                                                              10                                                                              10                                                                              --  --  --  --                                                                              --                                                                              10                                                                              10 10               II A-B-A block copolymer.sup.b                                                                    20                                                                              30                                                                              20                                                                              30                                                                              30                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --  --  --  --                                                                              --                                                                              --                                                                              -- --               III                                                                              A'-B'-A' block copolymer.sup.c                                                                 --                                                                              --                                                                              --                                                                              --  20                                                                              30                                                                              20                                                                              30                                                                              30                                                                              --  --  --  --                                                                              --                                                                              --                                                                              -- --               IV styrene-maleic anhydride                                                      copolymer.sup.d  80                                                                              70                                                                              70                                                                              60                                                                              --                                                                              80                                                                              70                                                                              70                                                                              60                                                                              --                                                                              100%                                                                              --  --  85                                                                              75                                                                              75                                                                              65 --               V  bromopolystyrene.sup.e                                                                         --                                                                              --                                                                              --                                                                              --                                                                              60                                                                              --                                                                              --                                                                              --                                                                              --                                                                              60                                                                              --  100%                                                                              --  --                                                                              --                                                                              --                                                                              -- 65               VI rubber modified styrene-maleic                                                anhydride copolymer.sup.f                                                                      --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --  --  100%                                                                              --                                                                              --                                                                              --                                                                              -- --               VII                                                                              emulsion draft polymerization                                                 product of an acrylic monomer on                                              a rubbery diene polymer.sup.g                                                                  --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --                                                                              --  --  --  15                                                                              25                                                                              15                                                                              25 25               __________________________________________________________________________     .sup.a control                                                                .sup.b Kraton GXT0650, Shell Chemical Co.                                     .sup.c Kraton 4119, Shell Chemical Co.                                        .sup.d Dylark 231, Sinclair Koppers (6.8% maleic anhydride)                   .sup.e Dylane 233                                                             .sup.f Inpact grade Dylark 250                                                .sup.g Acryloid KM 611                                                   

The compositions described in Table 1 were evaluated for physicalproperties and the results are reported in Table 2.

                                      TABLE 2                                     __________________________________________________________________________             1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18                __________________________________________________________________________    Notched Izod                                                                  Imp. (ft.lb./                                                                 in.n)    0.75                                                                             1.06                                                                             2.46                                                                             5.89                                                                             1.38                                                                             0.54                                                                             3.8                                                                              1.1                                                                              4.0                                                                              6.9                                                                              0.26                                                                             3.2                                                                              1.28                                                                             0.24                                                                             0.41                                                                             0.32                                                                             0.40                                                                             0.40              Heat Distortion               198-  185-                                                                             194-     208-  216-                                                                             217-                                                                             206-              Temperature (°F.)                                                               205                                                                              201                                                                              219                                                                              223                                                                              203                                                                              189                                                                              183                                                                              200                                                                              198                                                                              187                                                                              198                                                                              176                                                                              204                                                                              209                                                                              208                                                                              218                                                                              218                                                                              207               Gardner Impact                                                                (in./lb.)                                                                              45 47 114                                                                              225                                                                              46 -- -- -- -- -- 4.0                                                                              44.8                                                                             3.0                                                                              -- -- -- -- --                Tensile Strength                                                              (psi)    6600                                                                             5660                                                                             7720                                                                             6540                                                                             5500                                                                             5700                                                                             4400                                                                             6200                                                                             5500                                                                             5400                                                                             -- -- -- 8500                                                                             8100                                                                             9600                                                                             8800                                                                             8500              Elongation (%)                                                                         7.7                                                                              8.9                                                                              13 21 8.9                                                                              34 48 32 21 52 -- -- -- 6.1                                                                              9.1                                                                              9.6                                                                              20 24                __________________________________________________________________________

An analysis of this Table shows that the compositions of this inventionhave good impact strengths and relatively high heat distortiontemperature.

Other compositions may be prepared by using the following materials:

A. styrene-maleic anhydride copolymer prepared according to Example II,run 10 of U.S. Pat. No. 3,336,267.

B. A-B-A block copolymer prepared according to run B of U.S. Pat. No.3,431,323.

C. A'-B'-A' block copolymer of styrene-butadiene-styrene preparedaccording to Example II of U.S. Pat. No. 3,265,765.

D. emulsion graft polymerization product of an acrylic monomer and arubbery diene copolymer as prepared in U.S. Pat. No. 2,943,074, column4, emulsified polymer "B".

EXAMPLE II

The following compositions were prepared using procedures analogous tothose employed in Example I:

    ______________________________________                                        Sample No.       19    20    21    22  23  24                                 ______________________________________                                        Components                                                                    (parts by weight)                                                             I   poly(2,6-dimethyl-                                                            1,4-phenylene) ether                                                          (PPO, General Elec-                                                           tric Co.)        --    10  --    10  --  10                               II  A-B-A copolymer.sup.a                                                                          70    60  --    --  --  --                               III A'-B'-A' copolymer.sup.b                                                                       --    --  --    --  30  30                               IV  emulsion graft poly-                                                          merization product of                                                         an acrylic monomer on                                                         a rubbery diene poly-                                                         mer.sup.c        --    --  25    25  --  --                               V   styrene-maleic anhy-                                                          dride copolymer.sup.d                                                                          30    30  75    65  70  60                               ______________________________________                                         .sup.a Kraton GXT0650, Shell Chemical Co.                                     .sup.b Kraton 4119, Shell Chemical Co.                                        .sup.c Acryloid KM 611 Rohm & Haas.                                           .sup.d Dylark 232, Sinclair Koppers; crystal grade.                      

The compositions of Example II were evaluated for physical propertiesand the results are reported in Table 3.

                  TABLE 3                                                         ______________________________________                                                     19   20     21     22   23   24                                  ______________________________________                                        Notched Izod Imp.                                                             (ft.lb./in.n)  1.3    7.7    0.4  0.4  2.4  5.5                               Heat Distortion Temp.                                                         (°F.)   --     --     --   --   --   --                                Gardner Impact (in./lb.)                                                                     63      155   10   10   65   81                                Tensile Strength (psi)                                                                       5780   6100   8100 8500 4000 4700                              ______________________________________                                    

Obviously other modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that changes may be made in the particular embodiments of theinvention described which are within the full intended scope of theinvention as defined by the appended claims.

We claim:
 1. A thermoplastic molding composition which comprises:(a)from 40-95 parts by weight of a copolymer of a vinyl aromatic compoundand an α,β-unsaturated cyclic anhydride; and (b) from 10-50 parts byweight of an emulsion graft copolymer comprising (1) from 20-80% byweight of a backbone polymer of the units of butadiene or butadiene andstyrene, wherein the butadiene units are present in quantities of atleast 40% by weight of the backbone polymer, (2) 80-20% by weight of anacrylic monomer chosen from the group consisting of lower alkylmethacrylates, alicyclic methacrylates and alkyl acrylates, graftpolymerized to (1) and (3) 0 to 60% by weight of a styrene monomer graftpolymerized to (1) sequentially before the polymerization of (2).
 2. Athermoplastic molding composition which comprises from 60-75 parts byweight of a copolymer of styrene-maleic anhydride, from 10-40 parts byweight of an emulsion graft copolymer comprising (1) from 20-80% byweight of a backbone polymer of the units of butadiene or butadiene andstyrene, wherein the butadiene units are present in quantities of atleast 40% by weight of the backbone polymer, (2) 80-20% by weight of anacrylic monomer chosen from the group consisting of lower alkylmethacrylates, alicyclic methacrylates and alkyl acrylates, graftpolymerized to (1) and (3) 0 to 60% by weight of a styrene monomer graftpolymerized to (1) sequentially before the polymerization of (2) andfrom5-30 parts by weight of a polyphenylene ether resin.